[1] Harvard Univ, Massachusetts Gen Hosp, Sch Med, Dept Radiol,Div Musculoskeletal Radiol, Boston, MA 02114 USA
[2] Harvard Univ, Sch Med, Childrens Hosp, Dept Radiol, Boston, MA USA
[3] Harvard Univ, Sch Med, Childrens Hosp, Dept Biostat, Boston, MA USA
[4] Harvard Univ, Sch Med, Childrens Hosp, Dept Surg, Boston, MA USA
[5] Univ Montreal, Hop St Justine, Dept Biostat, Montreal, PQ H3T 1C5, Canada